When people drink a glass or mug of beer, frothing beer is believed to be preferable in terms of taste and eye-pleasing point of view. An amount of froth should not be so large but not so small, and a ratio of froth of 7:3 is said to be ideal. At any rate, when beer is provided in business such as in restaurants, applying an appropriate amount of froth is essential to heighten commercial value of beer.
A large number of inventions have been developed to generate froth in beer. One of the currently available and typical techniques is a beer server machine which has a nozzle with two output openings, one for beer and the other for froth. A stopcock is opened to one side to allow beer to be fed to a glass or the like via a beer output spigot, and after filling the glass with beer, the stopcock is flipped to the opposite side to feed froth remaining in a dispenser via a froth output spigot. With this arrangement, froth feeding takes time because the remaining froth is fed at a very low pressure. A proper amount of froth cannot be obtained if the temperature of beer is very low, or depending on the frequency of beer servings.
A separate frothing device may be sometimes used to assist frothing. Known frothing devices include one for squirting mineral water into beer fed in a glass or the like (Patent Document 1) or one for squirting a gas (Patent Document 2).
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006-298461
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2000-85894